When planning for retirement income, most conversations center around taxes, withdrawals, and long-term sustainability.
What often catches retirees off guard, however, is Medicare.
Many people assume their Medicare premiums are fixed or primarily age-based. In reality, premiums for Medicare Part B and Part D are influenced by income — and certain financial decisions can create ripple effects that show up later in the form of higher premiums.
This is sometimes referred to as the “Medicare domino effect.”
Let’s unpack how it works.
Understanding IRMAA
Medicare premiums are subject to what’s called the Income-Related Monthly Adjustment Amount (IRMAA).
IRMAA applies when your Modified Adjusted Gross Income (MAGI) exceeds specific thresholds set by Medicare. When income crosses one of these brackets, premiums for Part B and Part D increase.
Two important details often surprise retirees:
IRMAA operates in tiers. Even one dollar over a threshold can move you into the next bracket.
The calculation looks back two years. Your 2026 premiums, for example, are generally based on your 2024 tax return.
This two-year lag is where unintended consequences often arise.
Roth Conversions and Premium Spikes
Roth conversions are frequently discussed as part of long-term tax planning. Converting traditional IRA assets to a Roth IRA increases taxable income in the year of conversion.
While there may be strategic reasons to consider a conversion, the added income can also push MAGI into a higher IRMAA bracket.
The result? Medicare premiums may increase two years later — even though the conversion decision felt unrelated to healthcare at the time.
This doesn’t necessarily mean Roth conversions are inappropriate. It simply highlights the importance of evaluating the broader impact before making large income adjustments in a single year.
Capital Gains and Other Income Surprises
Roth conversions aren’t the only trigger.
Other income events can also affect Medicare premiums, including:
Selling highly appreciated investments
Selling real estate
Large required minimum distributions (RMDs)
Bonuses or deferred compensation payouts
Significant one-time business income
A year that feels financially positive — such as realizing strong capital gains — can create higher Medicare premiums down the road.
Again, the issue isn’t whether these moves are “good” or “bad.” It’s understanding that income decisions often have interconnected effects.
Why Planning Two Years Ahead Matters
Because Medicare premiums are based on income from two years prior, decisions made today may not show their impact immediately.
This timing disconnect can make the increase feel unexpected.
Coordinating tax planning, retirement withdrawals, Social Security timing, and Medicare considerations requires looking forward — not just at the current year’s tax bill.
Questions worth evaluating may include:
How close am I to the next IRMAA threshold?
Would spreading income over multiple years change the outcome?
How do Roth conversions fit within my broader income plan?
What other large income events are anticipated?
When viewed holistically, these elements can often be sequenced more thoughtfully.
The Behavioral Side: Unintended Consequences
Financial decisions rarely exist in isolation.
It’s common to focus on the primary goal — reducing future taxes, rebalancing a portfolio, or simplifying assets — without fully considering secondary effects.
This is a classic example of unintended consequences.
In retirement, where multiple systems intersect (tax code, Medicare rules, Social Security, investment income), a single decision can influence several areas at once.
Recognizing this interconnectedness encourages more deliberate planning.
Pulling It All Together
Medicare premiums are not solely determined by age. Income plays a significant role, and certain financial decisions can influence costs in future years.
Understanding IRMAA brackets, recognizing the impact of Roth conversions and capital gains, and planning with a multi-year perspective can help reduce surprises.
Retirement income planning is not just about how much you withdraw — it’s about how each decision interacts with the broader system.
If you would like to review how your income strategy may affect future Medicare premiums, our team at Flagship Financial Advisors is available to discuss how these pieces fit within your overall retirement framework.